Magnetic chuck.



Patented July 20, 1915.,

2 SHEETS-SHEET 1.`

W. S. GRIFFITH.

MAGNETIC CHUCK.

APPucATloN man APR.27, 1914.

Ifl I) llll Wmedww:

W. S. GRIFFITH.

MAGNETIC CHUCK.

APPucAUoN FILED APR.27,1914.

Patented July 20, 1915.

2 SHEETS-SHEET 2.

UNITED sTATEs PATENT oEEIoE.

WINFRED S. GRIFFITH, OF WORCESTER, MASSACHUSETTS, ASSIGNOR TO HEALD MACHINE COMPANY, 0F WORCESTER, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS.

MAGNETIC CHUCK.

Specification of Letters Patent.

Patented July 20, 1915.

To all h-0m it may concern.:

Be it known that I, IVINFRED S. GRIFFITH, a citizen of the United States, residing at lvorcester, in the county of Worcester and State of Massachusetts, have invented a new and useful Magnetic Chuck, of which the following is a specification.

This invention relates to a magnetic chuck of the type commonly used to hold the work in position on lathes, planers, milling and grinding machines, and other types of metal working machinery.

It is the object of my present invention to improve the details of construction of such magnetic chucks, thereby increasing their eliciency and also simplifying the construction and decreasing the cost of manufacture of the several parts.

With these objects in view my invention comprises certain devices, arrangements and combinations of parts which will be hereinafter described and more particularly pointed out in the appended claims.

A preferred form of the invention is shown in the drawings in which- Figure 1 is a-sectional elevation taken on the line 1-1 of Fig. 2; Fig. 2 is a top plan view of thel chuck shown in Fig. 1 with the face plate removed; Fig. 3 is a top plan view of the face plate; Fig. 4 is a partial plan view of a face vplate similar to that shown in Fig. 3, with work-holding devices secured thereto, and Figs. 5 and 6 are detail sectional views showing one of the workholding devices in inoperative and operative positions respectively.

Referring to Fig. 1, my improved chuck comprises a chuck body 10 having an up wardly extending shell 11 around its outer edge. This chuck body may be of the form which is best adapted to the work for which a particular chuck is designed, the chuck shownvin the drawings being of cylindrical form. Within the shell 11 there is a central projection 15 and thus serves to hold the face plate firmly upon the central post and upon the shell 11. Additional binding screws 17a (indicated in dotted lines in Fig. 4) may be located around the circumference of the chuck body, extending upwardly therethrough, and being threaded into the face plate, if the size of the chuck renders their use advisable. A cylindrical recess 22 is provided in the working face of the face plate, this recess being useful for centering purposes when the chuck is used upon a lathe. A plurality of pole pieces 18 are mounted in recesses in the face plate 14, being secured therein and magnetically insulated therefrom by a layer of relatively soft non-magneticl material 19. I have found that the metal commonly called expansion metal, from its property of expanding upon v cooling, is a suitable material for this purpose.

In assembling the face plate the pole pleces are held in a suitably constructed jig `so that they are properly spaced from the Walls of the recess in the plate 14, the melted expansion metal being thereafter poured into the spaces surrounding the pole pieces. It is desirable that the sides of the pole pieces should be roughened or serrated as shown in Fig. 1, so that the holding power of the expansion metal may be increased. Upon its underside the face plate 14 is provided with an annular recess 20 which is also filled with expansionmetal. As this recess is upon the lower side of the plate it is convenient to provide a connecting recess 21 through which the metal may flow from the upper side while it is filling the spaces around the pole pieces. This annular ring ofrelatively soft metal upon the lower side of the face plate serves several useful purposes. In the manufacture of these face plates it is customary to grind both faces of the plate to a plane surface after the pole pieces are inserted. As the expansion metal offers less resistance to the grinding wheel than the material of which the face plate and the pole pieces are formed, the annular ring will be cut away to a slightly greater depth than the other portions of the face plate. When the parts are assembled as shown in Fig. 1, this will concentrate the pressure exerted by the screws 17 upon the magnet cores 13, thus insuring a close contact of thev cores with the pole pieces before the expansion metal ring is seated upon the shell 11. A further advantage of this metal ring lies the fact thatits relative softness enables it toiorm a more closely fitting joint with the shell 11, thereby preventing the possible admission ofmoisture to the magnet'coils M. These coils, as shown in Figs.

`1 and 2, are of substantially rectangular formation, and-'fclosely surround the cores 13.

In the circular chucks which are designed l "particularly for use,v upon lathes and simllar machines, .I provide the contact .device shown in section in Fig. 1. This device comprises a ring 23 .of insulating-material secured to the bottom of the chuck body, havling mounted thereon two concentric rings l* A terminal post 26 is supported in the chuck.

24 and 25 of brass or'other suitable metal.

body byan'insulating bushing 27 and y extends downward through the ring 23 into ,the inner contact ring -25. A similar termi nalpost 28 extends downward through the chuck body and, -Where the arrangement of the ,coils will permit, passes drectly'through -f .inthe Same mannerv as does thepost 26.1

. -Where the position ofthe 4outer magnetcoil prevents this arrangement, Ifprovidegabrassplate .29- which is, radially .arraiifgifidvv 1n a recess in the insulating ring 23 affwhich has one end secured to the post` 28 and theft opposite end connected tothe .ringv 24', as by 'y a screw 30. As the .voltage at which 'these chucks'are operated varies in different es- ,ftablishments, I. arrangethe magnet' coils in two" or more groups, the coils in each group being' arrangedin series, andthegroups themselvesfbeing arrangedinl series or; .4 parallel according to the Vvoltage at which they-are' to be operated. f y

coils', are fai-rangedI in two groups, which or larger chucksin which" a Y -g'reaternumber of' coils is used,'.;the number of lgroups be' increased,so that'. thel 4p rope' number of coils-will-be 'included infrj l -may .be roughened or-gs'errated'upon their working faces if sofdesired. Thearms 31 "are formed of magneticl material and stand Th'e terminal posts 26and 28 provid'ecvon-A Vvenient conductorsto thev contact rings and .by changing the @connectionsfrom the VI vgroups to Athese posts .thearraugement of the coils maybe l'readily varied. Any suitabledevice maybe provided for transmittinlg current to. the contactrings.A

4has been heretofore customary in circular.. chucks to group the ,pole pieces in 'radial relation about thecenter of the chuck.

inthe' chuck shown in. the' drawings; 'the small 'articlesupon achuck, particularly' if 'agresser With this arrangement the poles have been close together at their innerends and widely i separated at their outer ends, the holding power of the chuck per unit of area thus decreasing as the diameter increased. To

avoid this disadvantage, I have provided the arrangement of' poles shown in the drawings in which all of the pole pieces are substantially equal lin width throughout vtheir length, the pole pieces being arranged in parallel relation and so proportioned in length that their outer ends shall all be subthe center of the chuck I arrange two of the pole pieces in radial relation to the center and placea pair of pole pieces of opposite 4polarity upon each side of the radial pole pieces. I furthermore extend one pole piece of each of the last named pairs beyond the center line of the chuck and provide these p p ole pleces `with lateral projections on their inner sides,- the inner faces of these pro- Jectlons and the ends of the radial pole ieces beingsubstantiallyl equally spaced rom the'center. In the preferred form I' also form the inner faces of the lateral pro# jections concentric with the center.. With this arrangement I am enabled to greatly increase the holding power ofthe chuck in 'the immediate vicinity of the center. With the pole pieces ,magnetized' in such a way that each alternate pole piece is of opposite polarity it will be seen that the path ofthe magnet-lines of force lies between adjacent pole pieces, and that lthe shell 11 and the central part -12 form no essential part of themagnetic circuit. Furthermore the face plate 14 is not essential to the completion of the' circuit and the chuck -will operate equally well when for any reason it is found magnetic material. rIn Figs. 4, 5 and VG I'have-shown an improved vdevice for centering 'and holding desirable to construct the'plate 14ofgnonf such `articles are of non-magnetic material.

.these arms are provided with upwardly projecting work-holding members 33, which normally in ,the -position shown. in Fig. 5.

As s'oon as the current is turned on, the

'magnetized pole pieces will draw'the. arms strongly toward'the face plate, bringin iso' pivoted to supports adjustably mounted upon the face plate.

Having thus described my invention it will be obvious that many changes and modifications can be made therein by one skilled in the art without departing from the spirit and scope of my invention as set forth in the claims, and I do not wish to be limited to the specific details herein disclosed, but

What I do claim is 1. A circular magnetic chuck having, in combination, a chuck body, a circular face plate, and a plurality of separate pole pieces mounted in said face plate and of opposite polarities when in use, said pole pieces being of substantially equal width throughout their length, but of different relative lengths, and being all secured in said face plate in substantially parallel relation but magnetically insulated therefrom, the outer ends of said pole pieces ,being at substantially equal distances from the periphery of the face plate, and the pole pieces of one polarity alternating with the pole pieces of the opposite polarity.

2. A magnetic chuck having, in combination, a chuck body having an outer shell, a4

face plate, and a plurality of pole pieces mounted in said plate but magnetically insulated therefrom, said face plate having a ring of relatively soft metal inserted in its lower face and forming the bearing surface upon the shell of the chuck body.

` 3. A circular magnetic chuck having, in combination, a face plate, and a plurality of .parallel pole pieces mounted in said face l plate but" magnetically insulated therefrom,

one pair of said pole pieces being radial to the center of said face plate, and an additional pair being each mounted parallel to one of the radial poles and having a projecv tion upon its inner side. concentric with the center of the chuck, whereby the ends of the two pairs of poles surround and are spaced substantially equally from the center of the chuck. 4

4. A magnetic chuck having, in combination, a chuck body, having a plurality of magnet cores supported therein, coils for said cores, a circular face plate, and a plurality of pole pieces mounted in but magnetically insulated from said face plate, one pair of said pole pieces being radial to the center of said plate', and two additional pairs being parallelto the radial poles, one pair on each side thereof, one pole of each of the center line and having a lateral projection on its inner side, with its inner face and the inner ends of the radial poles substantially equally spaced from the center.

5. A magneti-c chuck having, in combination, a face plate, and a plurality of work holding arms secured at one endy to said face plate, said arms being formed of magnetic material and having their operative ends normally spaced from said plate.

6. A magnetic chuck having, in combination, a face plate, and a plurality of work holding spring arms adjustably secured to the face of said plate, said arms being formed of magnetic material.

7. A magnetic chuck having, in combination, a face plate, a plurality of flat spring arms formed of magnetic material adjustably secured by one end to said face plate, and Work holding members mounted on the free ends of said arms, and spaced from the plate when in normal position.

In testimony whereof I have hereunto set my hand, in the presence of two subscribing Witnesses.

WINFRED s. GRIFFITH.

Witnesses:

C. FoR'REsT WEssoN, CATHARINEL I. HARTNETT.

last named pairs being extended beyond the 

